In a variety of medical applications, valves are used to control the inflow and outflow of fluids into and out of a patient's body. Such applications include, among others, blood transfusions, stomach evacuations, heart lung machine procedures, and colonic lavage for the removal of fecal impactions from a patient's bowels. In the case of colonic lavage, it is common that a first valve is connected in the liquid supply line of the lavage apparatus to control the inflow of water or other lavage liquid into a patient's colon for hydrating and loostening impacted fecal material. A second valve is connected in the drain line. This second valve usually is closed during fluid inflow to allow the bowels of the patient to fill with fluid. The second valve can then be opened to allow fluid and loosened fecal material to flow out of the patients colon to an appropriate receptacle.
Valves used in colonic lavage systems and, indeed, in other medical applications, are subject to a number of relatively severe operational constraints. First, such valves must be extremely reliable because the lives of patients can and often are dependent upon their flawless operation. In addition, the valves must be gentle in that they must open and close in such a way that fluid flow is not stopped or started abruptly, which can shock a patient's system or damage delicate tissues. This is particularly true in the case of colonic lavage procedures because colon walls are thin and subject to rupture under abrupt stresses. It is also important in colonic lavage procedures that valves used in the system have the ability to cause a rapid pulsing of the lavage inflow liquid to aid in the loosening of fecal impactions. In addition, such valves must be opened reliably and automatically in response to excess back pressure from the colon in order to prevent damage to the colon as a result of excess fluid pressure.
In the past, a variety of valves have been used in medical procedures such as those discussed above. In many cases, a sphincter valve design has been adopted because of its many advantages. In a sphincter valve, communication through the valve is closed by squeezing or collapsing a flexible tube within the valve through which the fluid passes. The valve is opened by releasing the flexible tube to allow the fluid to flow. This squeezing and releasing has been accomplished in a number of ways. In a heart lung machine, for example, the tube is squeezed and released by moving rollers that intermittently engage, compress, and roll along a short length of the tube. This action not only closes the valve, it also has the effect of pumping fluid intermittently through the tubing. In another type of sphincter valve, a mechanical plunger is actuated to engage and compress the flexible tube to close off communication therethrough.
One sphincter valve design that has proved itself reliable is the pneumatically controlled sphincter valve. Such valves have proven particularly useful in colonic lavage systems. In these types of valves, a short, flexible, collapsible tube is enclosed within a pressure chamber coupled to a source of compressed air. The tube is coupled or spliced into the lavage liquid delivery line to control lavage fluid inflow. A similar valve may be spliced into the waste drain line to control the flow of contaminated fluid from the patient's colon. When it is desired to close one of the valves, pressurized air is injected into the pressure chamber. This generates inward force that collapses the interior tube and shuts off the flow therethrough.
In the past, pneumatic sphincter valves have been constructed of a hard injection molded plastic outer shell having corresponding injection molded end caps that can be glued in place to form a generally cylindrical pressure chamber. A short tubular nipple communicates with the interior of the chamber and projects outwardly from the side thereof for selective delivery of pressurized air to the pressure chamber. Each of the end caps is molded with a short tubular coupler that extends and communicates through the end cap and that has an interior end within the chamber and an exterior end outside the chamber. A length of flexible surgical tubing is secured at its ends to the interior ends of the couplers communicating therebetween. The entire assembly is spliced into a liquid delivery or drain line by cutting the line if necessary and coupling the cut ends of the line to the exterior portions of the tubular couplers. Thus, fluid can flow from one section of the line, through the flexible tube within the chamber, and into the other section of the line. The tubular nipple is coupled to a source of selectively deliverable compressed air. When it is desired to shut the valve off, compressed air is injected into the pressure chamber, exerting pressure on the flexible tube within to compress and collapse the tube, thus shutting off the flow. For opening the valve, the pressure is simply released.
While the just described pneumatic sphincter valve design has proved useful and reliable, it nevertheless embodies certain problems and shortcomings inherent in its design. For example, the valve is relatively expensive to manufacture because key components are injection molded. Further, the valve is time consuming and thus expensive to fabricate because the internal flexible tube must be installed manually and the end caps and other components must be glued to the chamber by hand. The hard plastic shell of the chamber can shatter if dropped and is uncomfortable to the skin of a patient such that the valve cannot comfortably be laid or rested on the patient during use. Finally, since the flexible internal tube of the valve is separate and made of a different material than other valve components, it can, under certain circumstances, come loose from the couplers within the valve causing the valve to fail and risking contamination of the compressed air supply.
For these reasons, and particularly due to the expense of production and fabrication, conventional pneumatic sphincter valves have not been economical for use with disposable colonic lavage kits designed to be discarded after a single use. Accordingly, such disposable kits have been expensive and thus not easily available to lower income persons or patients on fixed incomes. There is thus a need for a reliable, unbreakable, and economical sphincter valve that can be used with colonic lavage and other medical procedures and discarded after use. It is to the provision of such a sphincter valve that the present invention is primarily directed.